title: Compression feedback devices over estimate chest compression depth when performed on a bed.
abstract: BACKGROUND
  CPR feedback/prompt devices are being used increasingly to guide CPR performance in clinical practice. A potential limitation of these devices is that they may fail to measure the amount of mattress compression when CPR is performed on a bed. The aim of this study is to quantify the amount of mattress compression compared to chest compression using a commercially available compression sensor (Q-CPR, Laerdal, UK). A secondary aim was to evaluate if placing a backboard beneath the victim would alter the degree of mattress compression.
  
  
  METHODS
  CPR was performed on a manikin on the floor and on a bed with a foam or inflatable mattress with and without a backboard. Chest and mattress compression depths were measured by an accelerometer placed on the manikin's chest (total compression depth) and sternal-spinal (chest) compression by manikin sensors.
  
  
  RESULTS
  Feedback provided by the accelerometer device led to significant under compression of the chest when CPR was performed on a bed with a foam 26.2 (2.2)mm or inflatable mattress 32.2 (1.16)mm. The use of a narrow backboard increased chest compression depth by 1.9mm (95% CI 0.1-3.7mm; P=0.03) and wide backboard by 2.6mm (95% CI 0.9-4.5mm; P=0.013). Under compression occurred as the device failed to compensate for compression of the underlying mattress, which represented 35-40% of total compression depth.
  
  
  CONCLUSIONS
  The use of CPR feedback devices that do not correct for compression of an underlying mattress may lead to significant under compression of the chest during CPR.
authors.affiliation: Warwick Medical School, University of Warwick, Warwick CV4 7AL, United Kingdom. g.d.perkins@warwick.ac.uk
authors.forename: Gavin D
authors.initials: GD
authors.lastname: Perkins
authors.forename: Laura
authors.initials: L
authors.lastname: Kocierz
authors.forename: Samuel C L
authors.initials: SC
authors.lastname: Smith
authors.forename: Robert A
authors.initials: RA
authors.lastname: McCulloch
authors.forename: Robin P
authors.initials: RP
authors.lastname: Davies
mesh_terms: D001513:Beds; D016887:Cardiopulmonary Resuscitation / Q000295:instrumentation* / Q000379:methods*; D019245:Compressive Strength; D004867:Equipment Design; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D005246:Feedback; D006801:Humans; D008348:Manikins; D013909:Thorax